some liverbearer females (guppies, platys, mollies, endlers) will die after birth due to the stress of giving birth...........I have not heard of anything you can do for them either..............Just a part of the cruelity of nature, i guess

after they give birth, you can try taking them out of the tank so that they aren't harassed by the males, that seems to help. Just give her a day or two alone. I have also found that if they live after the first drop they are much more likely to survive subsequent times.